The Grumman F9F Panther / Cougar

v1.0.4 / 01 apr 15 / greg goebel

* During World War II, the Grumman Aircraft Corporation of Bethpage, New
York, became famous for its naval piston-powered combat aircraft -- F4F
Wildcat, F6F Hellcat, and TBF Avenger. In the postwar period, Grumman
carried on the tradition into the jet age by introducing the "F9F Panther",
which performed distinguished service in the Korean War, and which was
followed by a swept-wing version, the "Cougar". This document gives a
history and description of the Panther and Cougar.

* At the end of World War II, most American aircraft manufacturers had
designs for jet aircraft on the drawing boards. Following work on several
concepts for pure jet and "mixed power" aircraft with both jet and piston
propulsion, engineers at the Grumman Corporation considered a two-seat night
fighter, the "G-75", something like the company's F7F Tigercat but powered by
Westinghouse J30 turbojets. Since this engine provided only a feeble 13.4 kN
(1,360 kgp / 3,000 lbf) of thrust, the G-75 had four engines, mounted in the
wings.

The G-75 lost the competition to the Douglas XF3D-1, which would emerge as
the "Skyknight", but as a backup plan the US Navy Bureau of Aeronautics
(BuAer) awarded Grumman a contract for two prototypes of the G-75, with the
military designation "XF9F-1", on 11 April 1946. As work on the G-75
progressed it was increasingly obvious that it was a loser, but Grumman had
also been working on an entirely different concept for a single-seat day
fighter, the "G-79". In an intriguing exercise in bureaucratic paperwork,
instead of formally canceling the G-75 program and awarding a new contract
for the G-79, the G-75 contract was simply amended to specify the G-79, with
three prototypes to be built.

Two of the prototypes, to be designated "XF9F-2", were to be powered by a
single Rolls-Royce "Nene" centrifugal-flow turbojet engine, with 22.3 kN
(2,270 kgp / 5,000 lbf) thrust and mounted in the fuselage. Efforts were
underway at the time to arrange license production of the Nene by Pratt &
Whitney (P&W) in the US as the "J42". Since the license arrangement hadn't
been finalized, as a backup plan the third G-79 prototype, designated
"XF9F-3", was to be powered by a similar but less powerful General Electric /
Allison J33 engine, with 20.5 kN (2,090 kgp / 4,600 lbf) thrust.

The first XF9F-2 performed its initial flight on 21 November 1947, with
Grumman test pilot Corwin H. "Corky" Meyers at the controls. The second
prototype flew on 26 November. Both were unarmed. The second prototype
crashed during carrier trials on 28 October 1948, but the development program
suffered no real delays. The Allison-powered XF9F-3 performed its initial
flight on 16 August 1948.

Hedging their bets, Navy brass decided to order both versions of the
"Panther", as the new fighter was called, specifying the production of 47
F9F-2s and 54 F9F-3s. The two variants were to be produced in parallel, with
the initial production items of both flying in November 1948. However,
license construction of the J42 / Nene by P&W was moving forward, rendering
the Allison-powered Panther unnecessary, and in fact all the F9F-3s were
either completed as or rebuilt to F9F-2 specification.

Initial deliveries of the F9F-2 to service units began in May 1949, and a
total of 564 was built, including those that started life as F9F-3s.
Underwing stores pylons were added about halfway through production; these
Panthers were known using the designation of "F9F-2B" for a time -- until all
earlier production was refitted with stores pylons, and then all were simply
referred to as F9F-2s.

* The F9F-2 was of all-metal construction, with a mid-mounted straight wing,
tricycle landing gear, and a "stinger"-type arresting hook under the exhaust.
The wing featured leading-edge and trailing-edge flaps. The tail assembly
was of conventional configuration, with a mid-mounted tailplane. There was a
small extensible bumper just ahead of the arresting hook. The main gear
hinged in the wings to retract towards the fuselage, while the nosewheel
retracted backwards. There was a split perforated airbrake just behind the
nosewheel doors. The nose and tail pulled off for maintenance.

The F9F-2 was powered by a J42-P-8 turbojet with 22.3 kN (2,270 kgp / 5,000
lbf) dry thrust and 25.6 kN (2,605 kgp / 5,750 lbf) boost thrust with water
injection; early production had the J42-P-6 with the same thrust, but a
different ignition system. The engine intakes were in the wing roots.
There were two spring-loaded auxiliary intake doors for takeoff and emergency
airflow positioned, somewhat surprisingly, on the spine of the aircraft's
midsection.

The wings folded hydraulically upward from just outboard the main gear;
oddly, the wing fold angle was well short of the vertical. 455 liter (120 US
gallon) fuel tanks were permanently mounted on the wingtips. The tip tanks
were not fitted originally to the prototypes, being initially trialed on the
first prototype and rolled into manufacturing with the 13th production F9F-2.
Including internal tanks and wingtip tanks, total fuel capacity was 3,498
liters (923 US gallons). The pilot sat on an ejection seat in a pressurized
cockpit under an all-round vision canopy that slid backwards to open. There
was a small step on the lower fuselage that could be slid out to help the
pilot get into and out of the aircraft.

The F9F-2 was armed with four 20 millimeter M3 Hispano-type cannon with 190
rounds per gun, fitted under the nose. The guns were aimed by a Mark 8
computing optical gunsight. The F9F-2 had no radar. It had four stores
pylons under each wing, with a heavy pylon inboard and three lighter pylons
outboard, for a total of eight pylons. The large pylon could handle up to a
450 kilogram (1,000 pound) bomb and was "wet", allowing carriage of a 568
liter (150 US gallon) drop tank. The outer wing pylons could each carry up
to a 125 kilogram (250 pound) bomb or a 12.7 centimeter (5 inch) "high
velocity air rocket (HVAR)"; it doesn't seem that HVARs were ever carried on
the large pylon, possibly because they were too close to the intakes and
rocket exhaust ingestion might have caused engine stalls. Total external
load was 900 kilograms (2,000 pounds) -- though in practice, the F9F-2 was
too underpowered to take off from a carrier deck with anything resembling a
full combat load. Engine improvements were clearly needed.

Although the prototypes had flown in natural metal finish, production
machines were painted in overall dark sea blue, the standard US Navy and
Marine color scheme of the day. Colorful trim was added as desired by
various squadrons.

* The F9F-2 was the first US Navy jet to go into combat, performing
airstrikes in support of UN forces fighting in Korea on 3 July 1950. The
Panther would score its first "kill" on 3 July 1950, when Ensign E.W. Brown
and LTJG L.H. Plog shared credit for the destruction of a Yakovlev Yak-9
piston-powered fighter. On 9 November 1950, Lieutenant Commander Tom Amen
claimed the destruction of a Russian-built Mikoyan MiG-15 fighter, the US
Navy's first jet-on-jet kill. Panthers would claim four or five more kills
against the MiG-15 and records show no losses of Panthers to the MiG-15 in
return -- but air combat statistics are notoriously dodgy, and these figures
might be taken with a grain of salt.

The Panther was not generally the equal of the faster MiG-15 in performance
and was mostly used in the attack role, but like its Grumman ancestors its
was extremely rugged, able to both dish out and take punishment. It became
the most heavily used jet fighter of the Navy and Marines during in the war.
It also became the mount of the US Navy "Blue Angels" flight demonstration
team in 1949, replacing Grumman F8F-1 Bearcats and becoming the first jet
flown by the Angels.

A number of F9F-2s were field-modified by the Navy to a photo-reconnaissance
configuration as a "stopgap solution", seeing service in Korea. These
machines had no cannon, the nose carrying a suite of vertical and oblique
cameras instead, and were designated "F95-2P". They served through most of
the war, operating as a complement to McDonnell F2H-2P Banshee photographic
reconnaissance machines.

Small wing fences, fitted after production in the field. The fences were
installed outboard of the engine intakes to improve low-speed
handling.

The F9F-4 prototype was converted from a production F9F-2 and performed its
initial flight on 5 July 1950. 109 production F9F-4s were built and the
Marines operated at least one squadron in Korea, but the Allison engine was
unreliable, and many of these were converted to the "F9F-5" configuration.

* The F9F-5 was effectively an F9F-4 with the stretched fuselage, taller
tailfin, and so on, but with an improved derivative of the Nene turbojet,
known as the Rolls-Royce "Tay" and built under license by P&W as the "J48",
instead of the Allison J33-A-16. The J48-P-6 engine fitted to the F9F-5
provided 27.8 kN (2,835 kgp / 6,250 lbf) dry thrust and 31.1 kN (3,175 kgp /
7,000 lbf) wet thrust. (Some sources hint that the Tay / J48 had
afterburning, but this claim is hard to confirm.)

The initial prototype F9F-5, a converted production F9F-2, performed its
first flight on 21 December 1949, with deliveries to the Navy and Marines
beginning in November 1950. The F9F-5 generally replaced the relatively
underpowered F9F-2 in service, and went into combat in Korea in late 1952.
The Blue Angels had already upgraded to the F9F-5 about a year earlier, in
late 1951.

A total of 616 F9F-5s was built, not counting F9F-4 conversions. Some F9F-5s
were delivered in anodized aluminum finish as something of an experiment, but
the metal didn't hold up against corrosion and Panthers went back to glossy
sea blue.

A total of 36 "F9F-5P" unarmed photo-reconnaissance machines was built as
well. The cannon were removed and replaced by vertical and oblique cameras.
The modified nose stretched the length of the aircraft by 37 centimeters
(14.6 inches) to 12.2 meters (40 feet). The F9F-9P also included an
autopilot to provide stability during photoshoots.

* The Panther was quickly relegated to Reserve service after the Korean War,
lingering on late into the decade. Some Panthers were modified as target
drones and designated "F9F-2D" or "F9F-5D" as appropriate, with others
modified as drone controllers and designated "F9F-2KD" or "F9F-5KD" as
appropriate; the drones remained in service into the early 1960s. The only
way to tell them from conventional Panthers was by the presence of a set of
blade antennas on the nose. There were a number of other conversions of
Panthers:

One F9F-3 was fitted with a nose turret armed with four 12.7 millimeter
(0.50 caliber) Browning machine guns, but the project was abandoned.

One F9F-4 was fitted with a "boundary layer control (BLC)" or "blown
flaps" system, in which engine bleed air was blown over the top of the
flaps to improve low-speed handling.

In 1952, one F9F-5 was fitted with a nose probe for hose-and-drogue
inflight refueling. The trials went well and the Navy became enthusiastic
about the concept, though no Panther would be fitted for inflight
refueling in operational service.

Panthers were also used for armament trials. A picture survives of an F9F-5
at the naval weapons test center at China Lake in California carrying four
pods of four 12.7 centimeter Zuni rockets, for a total warload of 16 rockets
-- a formidable punch in the attack role.

* The only foreign user of the Panther was Argentina, which received 24
refurbished F9F-2s in 1958. They were operated by the Argentine Navy from
ground bases. Four were destroyed on the ground in a 1963 coup that put the
army and navy at odds. The survivors performed border patrols in 1965 during
a period of troubles with Chile. All were grounded due to lack of spares in
1969.

* At the outset of the F9F program, the Navy had pressed Grumman to consider
a swept-wing version, but in the face of inexperience with swept-wing
aerodynamics at the time, the company's engineers were uncertain of how to
proceed; the swept-wing F9F stayed on the back burner for the time being.
The Korean War and the MiG-15 brought it to the front burner, and in March
1951 the US Navy awarded Grumman a contract for a swept-wing F9F, which was
given the company model number of "G-93".

Three F9F-5s were modified on the production line as G-93 prototypes, with
two of these machines being flight prototypes and the third a static test
airframe. The program moved along quickly, the F9F-5 being a mature aircraft
and much having been learned about swept wings in the previous few years.
The initial flight of the "F9F-6" was on 20 September 1951, with Grumman test
pilot Fred C. Rowley at the controls.

The new variant was different enough from the F9F-5 to be given a new name:
"Cougar". The Cougar featured a wide range of improvements:

A 35-degree swept wing, with leading and trailing edge flaps of wider
chord, and no wingtip tanks.

Spoilers for yaw control on the upper wing, and full-chord wing fences.

An all-moving ("all-flying") swept tailplane.

Larger airbrakes and rudder.

Engine intakes moved forward.

A fuselage stretch of 60 centimeters (2 feet) to add fuel storage and
help compensate for the loss of the wingtip tanks. However, even with
the stretch, and the addition of bladder-type fuel tanks in the wing
leading edge, the fuel capacity was reduced by 8% to 3,483 liters (919 US
gallons).

The Cougar retained other elements of the Panther, such as the quad 20
millimeter cannon and J48 engine. Although early Cougar production was
fitted with the J48-P-6A variant, which was the same as the J48-P-6 with some
fixes, later F9F-6 production featured the J48-P-8, with a max thrust of 32.2
kN (3,290 kgp / 7,250 lbf).

Initial service deliveries were in late 1952. Pilots were delighted with the
improved performance of the Cougar, and surprisingly it turned out to have
better carrier handling than the Panther. No doubt Navy and Marine pilots
were eager to take on MiG-15s with a machine that could fight on more equal
terms, but the Cougar didn't reach combat before the war ended in July 1953.

646 F9F-6 Cougars were built into 1954. They were delivered in classic Navy
overall sea blue colors, but generally updated to the new standard of gull
gray on top and white on the bottom. Many were refitted in service with a
UHF direction finder in a fairing under nose, and some were fitted with a
nose inflight refueling probe. On 1 April 1954, three probe-equipped F9F-6s
set a transcontinental speed record by flying coast-to-coast in under four
hours, the best time being 3:45:30 for a distance of 3,925 kilometers (2,438
miles).

* A total of 60 "F9F-6P" unarmed photo-reconnaissance machines with a camera
nose and no cannon was built in 1954 and 1955. The camera nose stretched the
aircraft by 22 centimeters (9 inches) to 12.86 meters (42 feet 2 inches).
Some were refitted with nose inflight refueling probes.

They were followed by 168 "F9F-7s" with the Allison J33-A-16A engine. As
with the F9F-4, the Allison engine proved unreliable, and 50 of these
machines were delivered with the J48 engine, making them indistinguishable
from F9F-6s. Most F9F-7s that were delivered with the Allison engine were
refitted with the J48 as well.

The final single-seat fighter version of the Cougar, the "F9F-8", was
introduced in 1954. It featured a 20 centimeter (8 inch) fuselage stretch
with a larger fuselage fuel tank; a reinforced canopy; and a redesigned wing,
with greater area and reduced thickness to improve handling and provide more
wing fuel tankage. Fuel capacity was increased to a total of 4,029 liters
(1,063 US gallons). The F9F-8 was powered by a J48-P-8A or J48-P-8C engine,
with the same thrust as the J48-P-8, but with some minor improvements.

A total of 601 F9F-8s was built from 1954 to 1957. Late production was
fitted with a nose inflight refueling probe; it appears that earlier
production was refitted with the probe as well, and that the F9F-8 was also
refitted with the UHF homing system in an undernose fairing. Late production
F9F-8s could also carry four Sidewinder air-to-air missiles (AAMs), two under
each wing, and some earlier production was refitted with Sidewinder
capability as well.

The Blue Angels traded in their F9F-5 Panthers for F9F-8 Cougars in 1954;
they had been handed F9F-6s in 1953, but demand for the Cougar at the time
was intense, and they were promptly grabbed for operational service. The
Angels flew the F9F-8 up to 1957, when it was replaced with the Grumman F-11F
Tiger.

A number of F9F-8s were modified as "F9F-8B" tactical nuclear bombers, fitted
with a "Low Altitude Bombing System (LABS)". A total of 110 "F9F-8P" unarmed
reconnaissance machines with a swollen "duck's bill" camera nose were built
as well. They could be fitted with a nose refueling probe.

The last production version of the Cougar was the "G-105" or "F9F-8T", a
tandem-seat trainer. It featured a fuselage stretch of 86.4 centimeters (34
inches) and a single rearward-sliding canopy. There was a windscreen between
the cadet pilot's seat in front and the instructor's seat in back; armament
was reduced to two cannon. Initial flight of the F9F-8T was on 4 April 1956.
The US Navy had planned to adopt a navalized version of the Lockheed T-33
trainer, the "T2V-1 Sea Star", and had initially not been very interested in
the F9F-8T. However, the Sea Star program ran into troubles and the F9F-8T
began to seem more attractive, with the Navy obtaining a total of 399
F9F-8Ts.

Most F9F-8Ts were refitted with a nose refueling probe and some were wired
for Sidewinder AAMs, though in fact they rarely carried them. A
night-fighter version with AAM armament was considered but not adopted, and
an improved trainer with a P&W J52 turbojet was also considered but rejected.

* The Cougar was regarded as a fine aircraft, very rugged and reliable, with
excellent handling. Aircraft design was moving very rapidly in the 1950s,
however, and Cougar fighters were out of first-line service by the end of the
decade. They lingered in Reserve service into the mid-1960s. After
retirement from squadron service, Cougars were used as drones -- including
the "F9F-6K", "F9F-6K2", and "F9F-8K" -- and drone directors -- including the
"F9F-6D", "F9F-6PD", and "F9F-8D".

The US military services adopted a uniform aircraft designation system in
1962, and such Panthers as were still in operation at the time were
redesignated as follows:

The F9F-8T / TF-9J remained in training service into 1974. Four were flown
in Vietnam on fast spotter missions. A number of Cougars remain on static
display, but it doesn't appear any are flying any longer.

* As with the Panther, a number of Cougars were used for test and trials:

Two F9F-7s were modified for "flexdeck" landing trials in 1956. The idea
was to have a carrier deck with a padded surface and allow aircraft to
belly land, permitting the elimination of the landing gear and reducing
aircraft weight. The landing tests actually worked out okay, but the
concept suffered from a flaw that seems obvious in hindsight: aircraft
without landing gear couldn't land anywhere but on a flexdeck, and they
were a pain to handle after they landed. The concept was abandoned.

Several F9F-8Ts were used for ejection seat tests, with the rear canopy
section cut open to permit firing of the ejection seat.

The only foreign user of the Cougar was once again Argentina, which obtained
two hand-me-down US Navy F9F-8Ts in 1962. They were withdrawn from service
in 1971.